It is known that containers made of plastics materials can be packaged in groups, each group comprising a plurality of containers. In particular, such containers contain foodstuffs, such as yoghurts, compotes, or the like. A first packaging option is to have the containers detached from one another but grouped together in the same packaging, e.g. in a case or in stretch wrapping that holds them together. With such an option, in order to eat or drink the contents of the containers, the user must extract the containers from the case or else remove the wrapping. Such packaging is relatively costly because it requires an external element (case or wrapping). In addition, the handling required of the user is relatively demanding because, for example, once the wrapping has been removed, the containers are no longer grouped together and can no longer be handled as a single unit. In addition, the case or the wrapping constitutes waste.
To overcome those drawbacks, it is known that it is possible to manufacture containers that are connected together via their rims.
Devices for connecting containers made of plastics material together via their rims are known, for example, from Patent Documents FR 2 532 240 A1, DE 199 21 033 A1, and EP 0 050 083 A1. With such devices, containers that are manufactured separately by thermoforming or by injection molding are connected together.
Another possibility is to thermoform the containers from a single sheet of plastics material, with their rims remaining substantially in the initial plane of the sheet. For example, the containers are manufactured from the same sheet that is driven stepwise while being unreeled from a reel, or else the containers are manufactured in groups, each group being made from a sheet or panel of plastics material. To make it easier to separate the containers from one another, nicks or scores are formed in the zones defined by said rims.
Grouped-together containers that are easy to use are thus obtained inexpensively. However, the difficulty lies in how to succeed in breaking the lines along which the rims are connected together. To overcome that difficulty, the thermoplastic material that is chosen is a material that is both thermoformable and also easily breakable. For that reason, such containers are, in general, made of polystyrene. However, polystyrene is relatively expensive and is harmful to the environment to a certain extent, if only because it is difficult to recycle. However, other materials that have the properties required for forming containers, e.g. containers that are suitable for containing foodstuffs, do not necessarily have that capacity to break easily when they are nicked or scored. That applies, for example, to polypropylene.